a) Field of the Invention
The present invention relates to retaining wall blocks that can be used as landscaping elements to construct nice-looking, straight or curved retaining walls or edging.
The invention also relates to units made of a plurality of such blocks integrally connected to each other in line.
b) Brief Description of the Prior Art
Retaining wall blocks, also called "garden stones", are well known products that are commonly used to construct earth retaining wall structure, terrace walls, patio or side walk edging, flower bed borders and the like.
In Canadian patent No. 941,626 issued in 1974 to Giuseppe RISI, there is disclosed a concrete molded block of rectangular shape, provided with a groove extending centrally across its bottom flat surface and with a matching tongue extending centrally across its top flat surface. In use, these blocks can be stacked onto similar blocks extending in line with the tongues of the underlying blocks extending into the grooves of the overlying blocks. Since these tongues and grooves are centrally positioned, the front surfaces of all the stacked blocks extend in a same plane.
In Canadian patent No. 1,182,295 issued to the present inventors, it is suggested to shift the tongues and grooves of blocks like those disclosed in Canadian patent No. 941,626, so that each row of blocks stacked onto another row of blocks extending below, is automatically uniformly set back from the next below row of blocks.
In both cases, the blocks that are stacked can be slid laterally with respect to each other but cannot be slid forwards or rearwards because of their tongue-and-groove connection. Such a locking of the blocks against any transversal displacement substantially reinforce the wall in the direction where it is the most subject to deformation. However, because of their rectangular shape, the blocks disclosed in both of the above mentioned patent can only be used to construct straight walls.
To solve this problem, Canadian laid-open patent application No. 2,019,033 published in 1991 in the name of BLOCK SYSTEMS INC. discloses a retaining wall block of trapezoidal shape, having a locking that extend downwardly at the rear of its bottom surface. Due to the trapezoidal shape of the blocks, one may construct not only straight wall but also inwardly or outwardly curved wall. However, because of the very specific position of the locking flange, any wall that is built from such blocks is necessarily inclined, because every horizontal row of blocks is automatically set back from the adjacent row of blocks extending below.
U.S. Pat. No. DE 311,444 of 1990 in the name of Paul J. FORSBERG discloses a retaining wall block of trapezoidal shape, that can also be used to construct straight or serpentine walls. Depending on the relative angular position of the blocks of each horizontal course of blocks with respect to each other, one may indeed build a straight or serpentine wall with convex and/or concave surface. In this design patent, no reference is made to locking means to connect each horizontal row of blocks to the next underlying row. However, holes and cavities are provided in the blocks, probably for the purpose of connecting such locking means thereto.